I was going to suggest letting the kids make their own pizzas. This may be more trouble than you want to get yourself into with a bunch of 6 year olds. But it certainly would keep them occupied for awhile. Buy some small pizza crusts, cheese, and various toppings (pepperoni, bacon, veggies, etc.).
If the idea is for you to do as little as possible, then just go with something easy -- pizza or sandwiches or something.